Chem 103 Exam #1 Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. Which of the following can act as a Bronsted-Lowry base, but not as a Bronsted-Lowry acid? a. HPO 4 2- b. H 2 O c. NH 4 d. PO 4 3- e. HSO 4-2. Methylamine, CH 3 NH 2, acts as a weak base in water. The products of the reaction are _ and _. a. OH - and CH 3 NH 3 b. H 3 O and CH 3 NH 3 c. H 3 O and OH - d. OH - and CH 3 NH - e. H 3 O and CH 3 NH - 3. One water molecule can donate a proton to another in a process called _; the equilibrium constant expression for this reaction is _. a. neutralization; b. autoionization; c. protonation; d. hydrolysis; e. autoionization; [H 3 O ][OH - ] 4. A solution is not neutral. Which one of these statements is true? a. [H 3 O ] = 1.0 10-7 M b. [H 3 O ] = [OH - ] c. [H 3 O ][OH - ] = 1.0 10-7 d. [OH - ] = 1.0 10-7 M e. [H 3 O ][OH - ] = 1.0 10-14 5. In a 1.2 M solution of KOH, a strong base, [H 3 O ] = _,and [OH - ] = _. a. 1.0 10-7 M; 1.0 10-7 M b. 8.3 10-15 M; 1.0 10-14 M c. 8.3 10-15 M; 1.2 M d. 1.2 M; 8.3 10-15 M e. 1.2 M; 1.2 M
6. An acidic solution is diluted until [H 3 O ] is exactly half as much as before. The ph of the solution is now _ than before. a. 2.00 higher b. 0.69 higher c. 0.30 higher d. 0.30 lower e. 2.00 lower 7. Arrange the solutions in order of increasing acidity: I a solution with [H 3 O ] = 4.2 10-6 M II III lemonade, ph = 2.65 0.25 M nitric acid IV pickle juice, ph = 3.10 a. I-IV-II-III b. II-IV-III-I c. III-II-IV-I d. IV-I-II-III e. III-II-I-IV 8. Consider a 0.50 M solution of HNO 2, a weak acid with K a = 4.5 10-4. Which statement is true? a. [H3O ] > 0.50 M. b. The acid is mostly ionized. c. ph = 3.35. d. ph = 0.32. e. ph > 0.32. 9. The ph of a solution of a 0.15 M solution of HOCl is 4.14. What is the K a for HOCl? a. 5.7 10-2 b. 8.8 10-3 c. 4.8 10-4 d. 7.2 10-5 e. 3.5 10-8 10. The ph of a 0.172 M solution of benzoic acid (pk a = 4.20) is a. 2.48. b. 3.44. c. 4.37. d. 4.96. e. 5.63. 11. Calculate the ph of a 0.051 M solution of sodium lactate. The K a for lactic acid is 1.4 10-4. a. 1.29 b. 2.57 c. 8.28 d. 11.43 e. 12.71 12. Which of the following is a Lewis acid but not a Bronsted-Lowry acid? a. acetic acid b. NH 4 (aq) c. HCO 3 - (aq) d. CO 2 e. CO 3 2-
13. A buffer solution may result if K 3 PO 4 is mixed with a. HCl. b. K 2 HPO 4. c. NaOH. d. either HCl or K 2 HPO 4. e. either K 2 HPO 4 or NaOH. 14. A buffer solution is one which a. contains more than the expected amount of solute for a particular temperature and is therefore unstable. b. contains the maximum amount of solute possible for a particular temperature. c. changes color upon addition of strong base. d. contains an equal number of hydronium and hydroxide ions. e. resists changes in ph upon addition of acid or base. 15. To make a buffer using acetic acid one would add a. carbonic acid. b. sodium acetate. c. sodium chloride. d. ammonium chloride. e. ammonium phosphate. 16. A buffer solution is 0.080 M in lactic acid (K a = 1.8 10-4 ) and 0.070 M in sodium lactate. The ph of the solution is a. 2.86. b. 3.68. c. 3.80. d. 4.18. e. 4.62. 17. Which acid, in combination with its conjugate base, would be the best choice to make a buffer of ph = 4.20? a. acetic acid (K a = 1.8 10-5 ) b. benzoic acid (K a = 6.3 10-5 ) c. formic acid (K a = 1.8 10-4 ) d. hydrofluoric (K a = 7.2 10-4 ) e. nitrous acid (K a = 4.5 10-4 )
18. A buffer solution is 0.500 M in ascorbic acid and 0.500 M in sodium ascorbate. Its ph is 4.10. After addition of 10 ml of 1 M NaOH to 1.00 L of this buffer, the most likely value of the ph is a. 4.08. b. 4.10. c. 4.12. d. 5.95. e. 10.15. 19. Which of the following indicator(s) would be most suitable for the titration of acetic acid (pk a = 4.74) with NaOH? a. bromothymol blue (transition range ph 6 to 8) b. methyl red (transition range ph 4 to 6.3) c. phenolphthalein (transition range ph 8.3 to 11) d. all of the above e. none of the above 20. A 50.00 ml sample of 0.0950 M acetic acid (K a = 1.8 10-5 ) is being titrated with 0.0848 M NaOH. What is the ph after 28.00 ml of NaOH has been added? a. 5.04 b. 4.74 c. 4.44 d. 3.18 e. 3.06 21. Isotonic saline solution is 0.154 M NaCl(aq) What is the solubility of AgCl (K sp = 1.8 10-10 ) in such a solution? a. 2.8 10-11 M b. 1.2 10-9 M c. 5.3 10-6 M d. 3.4 10-5 M e. 0.077 M 22. In which of the following would calcium phosphate have the greatest solubility? a. 0.1 M aqueous sodium phosphate b. distilled water c. 0.1 M aqueous calcium nitrate d. saturated aqueous calcium hydroxide e. 0.1 M aqueous phosphoric acid 23. The solubility of silver chloride in water is increased by the addition of NH 3. Why? a. The solubility of many salts is affected by the ph of the solution. b. The formation of complex ions displaces the solubility equilibrium to the right. c. The solubility of most salts increases as temperature increases. d. Some insoluble compounds are amphoteric. e. A common ion displaces the solubility equilibrium toward the undissolved solute.
24. What is the largest mass of solid NaCl that can be dissolved in 1.000 L of 5.00 10-3 M AgNO 3 without a precipitate of AgCl forming? K sp for AgCl is 1.8 10-10. a. 0.78 mg b. 86 g c. 13 g d. 2.1 g e. 36 ng 25. A mixture of two metal ions in solution is to be separated by selective precipitation. As the concentration of the precipitating ion is increased, which metal ion precipitates first? a. The one with the lower value of K sp for its precipitate b. The one with the higher value of K sp for its precipitate c. The one present at higher concentration d. The one present at lower concentration e. Cannot answer the question without more information Short Answer 26. a. Explain why the solubility of carbonates and phosphates is increased by lowering the ph, but the solubility of chlorides is unaffected by lowering the ph. b. The solubility of copper(ii) carbonate is dramatically increased by the addition of NH 3, but the solubility of copper(ii) phosphate is not. Referring to the data below, explain why. K sp for copper(ii) carbonate = 2.5 10-10 K sp for copper(ii) phosphate = 1.4 10-37 K f = 1.1 10 13 Cu 2 (aq) 4NH 3 (aq) Cu(NH 3 ) (aq) 27. A solution contains 0.100 M Pb(NO 3 ) 2 and 1.00 10-5 M AgNO 3. It is intended to separate out the silver by selective precipitation of AgI. What is the maximum percentage of the total silver that can be recovered free of contamination by PbI 2? (K sp for AgI = 1.5 10-13 ; K sp for PbI 2 = 8.7 10-9 ).